Acanthamoeba keratitis infections of the cornea are being recognized with increasing frequency in all parts of the world due to widespread use of the soft contact lenses. Acanthamoeba is a small free-living amoeba found in soil, fresh water or sea water. Acanthamoeba infections are resistant to various antiprotozoal, antifungal, antiviral and antibiotic drugs, necessitating early diagnosis and corneal transplant as the only choice for treatment to avoid blindness. The ability of Acanthamoeba to form the drug resistant mature cysts is mainly responsible for the recurrence of the symptoms after penetrating keratoplasty. The use of immunosuppressive drugs allows opportunistic organisms like Acanthamoeba to colonize and cause chronic granulomatous encephalitis in brain or keratitis in cornea. The mechanism by which Acanthamoeba produces these infections has not been investigated in detail. Extensive studies have been carried out on the pathogenicity of the parasitic Entamoeba histolytica, which causes dysentery, colon ulceration and hepatic abscesses. The results indicate that the amoeba damages host cells by multiple mechanisms including the use of secreted enzymes like collagenases, cytotoxins with protease-like activity, contact dependent cytolysis due to phospholipases or amoebapores, phagocytosis and destruction of host inflammatory cells. We propose to survey the occurrence of some of these mechanisms during the in vitro interaction of axenically grown Acanthamoeba species with rabbit corneal cell line SIRC, primary cultures of rabbit corneal tissues and other cell lines. Specifically, the in vitro interaction of Acanthamoeba with host inflammatory cells like polymorphonuclear neutrophils and its effect on the destruction of monolayers of corneal cells will be investigated during the present pilot study period. We will test the effect of various antifungal drugs like polyoxinD, Nikkomycin or calcofluor white as well as nonsteroidal antiinflammatory drugs like piroxicam & ibuprofen during the growth and encystment of various strains of Acanthamoeba. Since different strains differ in drug susceptibilities, these in vitro drug studies may eventually lead to the design of an effective treatment for Acanthamoeba keratitis.